Optimising the effects of rigid ankle foot orthoses on the gait of children with cerebral palsy (CP) – an exploratory trial

Abstract

Purpose: This exploratory trial investigated the effects of rigid ankle foot orthoses (AFO) with an optimally cast Angle of the Ankle in the AFO (AAAFO) on the gait of children with Cerebral Palsy (CP), and whether tuning of the AFO - Footwear Combination (AFO-FC) further affected gait. Methods: Eight children with CP underwent gait analysis and tuning of their AFO-FCs using a 3-D motion analysis system. Comparisons were carried out for selected gait parameters between three conditions - barefoot, non-tuned AFO-FC and tuned AFO-FC. Results: In comparison to barefoot gait, walking with a non-tuned AFO-FC produced significant (p < 0.05) improvements in several key gait parameters. Compared to the non-tuned AFO-FC, on average a tuned AFO-FC produced a significant reduction in peak knee extension and knee ROM during gait. However, when examined as case studies, it was observed that the type of gait pattern demonstrated while wearing a non-tuned AFO-FC affected the outcomes of tuning. Conclusions: The findings of the current study indicate the potential benefits of using rigid AFO-FC with optimal AAAFO and tuning of AFO-FCs. This study emphasises the need for categorising children with CP based on their gait patterns when investigating the effects of interventions such as AFOs. Implications for Rehabilitation Rigid ankle foot orthoses (AFO) cast at an optimal angle to accommodate the length of gastrocnemius muscle may positively influence walking in children with Cerebral Palsy (CP). Tuning of the AFO-Footwear Combination (AFO-FC) has potential benefits to the walking of children with CP, depending on their gait abnormalities. When investigating the effects of interventions such as AFOs, it is important to categorise children with CP based on their gait abnormalities.

The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses

“…Also comparable to our results, the tuned AFO-FC in the Jagadamma study [12] resulted in an increased internal peak knee extensor and ankle plantar flexion moment, whereas the peak hip moment remained unchanged. While we did expect to see these changes at the ankle and knee joints, the unchanged internal hip moment between conditions was in contrast to our hypothesis.…”

“…In our study, subjects may have positioned the thigh such that the ground reaction force was aligned close to the hip joint at midstance, independent from shank kinematics, therewith showing similar internal hip joint moments between heel height conditions at this stage. Although AFO-FC heel height manipulations and the resulting changes in joint angles and moments found in Jagadamma's studies [11,12] were smaller compared to our study, the nature of their effects was similar. Hence, our study confirms the responsiveness of the SVA to changes in AFO-FC heel height, though providing a more systematic change of heel height and, additionally, analyzing the effect of adjusting footplate stiffness.…”

“…A recent study of Jagadamma et al [12] showed the effects of tuning rigid AFOs on joint kinematics and kinetics in children with spastic Cerebral Palsy. In that study, tuning was based on inclining the SVA, starting from 128, until the ground reaction force alignment during stance was closest to normal.…”

“…Accordingly, the SVA at midstance may be an important and relatively simple parameter to evaluate the effects of adjustments to the AFO-FC during its tuning process [8,13], also because information on the ground reaction force and calculations of joint moments are not always available in clinical practice. Several studies in patients with neurological disorders report the SVA, and describe a normalization of gait parameters following changes of the heel-sole differential [11,12,14,15]. However, in all available studies, the SVA was measured while the patient was in a static position, whereas there is no evidence showing that the SVA in this position represents the SVA at midstance [8].…”

“…Tuning of the AFO optimizes the alignment of the ground reaction force with respect to the joint rotation centers, enhancing normalization of the joint kinematics and kinetics [8][9][10][11][12]. Such tuning can be described as the process in which the properties of an AFO-Footwear Combination (AFO-FC) are manipulated.…”